The present invention relates to an image forming apparatus and an exposing apparatus which exposes a sheet-shaped light sensitive material fixedly held on an outer peripheral surface of a drum rotating at high speed on the basis of image data.
Conventionally, in the exposing apparatus, as a method of fixing the sheet-shaped light sensitive material on a drum, a method based on electrostatic adsorption, a method of fixing by holding mechanically an end of the sheet-shaped light sensitive material, a method of fixing by holding an end with an adhesive tape or the like, and a method of fixing by air suction are known.
Recently, in the exposing apparatus stated above, to reduce exposure time has been demanded.
As a result of studying to reduce exposure time by making the rotational speed of the drum higher, it has been found that image unevenness tends to happen in the method of fixing an end of the sheet-shaped light sensitive material as the conventional technique.
Especially, in the case that the sheet-shaped light sensitive material is a silver halide photographic light sensitive paper, a part of the central portion of the silver halide photographic light sensitive paper sometimes floats up and the floating section shifts out of the depth of field of a light beam, because the stiffness of the silver halide photographic light-sensitive paper is low, differing from a photographic film.
Further, in the case that a paper size is greater than A3 size, since a region distant from the ends is wider, a part of the region tends to float up to an extent that the floating section shifts out of the depth of field of a light beam.
Furthermore, when producing a color proof, if the image unevenness as that stated above takes place, there may be a problem that the reliability as a color proof is lowered.